You can create price alert here, copy coupons and view price history. You probably want to know what is the best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Android 6.0 5.5 inch Helio X20 Deca Core 2.1GHz Fingerprint Scanner 5.0MP + 13.0MP Cameras
Price history and price alert
Price history (for all/most countries) for Xiaomi Redmi Note 4X 4/64GB Golden is here.
Price records source(s): Gearbest
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You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).